Alkenylphosphonic acid esters have a basic skeleton found in natural products and are known to exhibit physiological activity by interaction with an enzyme. Alkenylphosphonic acid esters may also be used as a raw material for performing Horner-Emmons addition reaction with a carbonyl compound and, therefore, are widely used for the synthesis of olefins.
A method is generally known to produce an alkenylphosphonic acid ester with the formation of carbon-phosphorus bond, in which the corresponding halide is subjected to substitution with a dialkylphosphite. This method requires the addition of a base for capturing hydrogen halide produced as the reaction proceeds. Thus, a large amount of a hydrogen halide salt is produced as by-product. In addition, the unsaturated halogen compound used as the starting material is not industrially easily feasible and is toxic in nature. Therefore, the above method is not advantageous from the industrial point of view.
Recently, a method was found in which a non-cyclic secondary phosphonic acid ester is added to an acetylene compound in the presence of a palladium catalyst (Journal of American Chemical Society, vol. 118, p. 1571 (1996); Japanese patent No. 2775426). The selectivity attained by this method is low. Further, the phosphonic acid ester compound, the major product of this method, is non-cyclic. In the reaction with the terminal acetylene group, the phosphorus is bonded to the carbon atom located on an inner side from the terminal carbon of the carbon-carbon unsaturated bond to give an α-addition product rather than β-addition product in which the phosphorus is added to the terminal carbon.
The present invention is aimed at the provision of a novel alkenylphosphonic acid ester and a simple process for the preparation thereof by the use of secondary cyclic phosphonic acid ester as the starting material.